直接从内置类型继承而不是从Python中的包装类继承

Question

我正在读马克·皮尔格林的Dive Into Python，并且已经进入了关于继承的部分。在section 5.5中，Pilgrim提到了从包装器类UserDict继承与从内置dict类型继承之间的区别。在

我很难理解为什么有人会费心于包装类。。。从UserDict包装器类（或任何其他UserXxx类）继承有什么好处？在

非常感谢您的意见。谢谢！在

Answer 1

你说得对：

The need for this class has been largely supplanted by the ability to subclass directly from dict (a feature that became available starting with Python version 2.2). Prior to the introduction of dict, the UserDict class was used to create dictionary-like sub-classes that obtained new behaviors by overriding existing methods or adding new ones.

注意第一句话。这来自UserDict的documentation。在

哦，在Python3中它不见了。在